The autonomic nervous system includes the sympathetic and parasympathetic pathways. Stimulation of nerves in these pathways affects cardiac operation and/or function. In general, stimulation of the sympathetic nerves causes an increase in heart rate and inotropy (contractility) and hence cardiac output. In contrast, stimulation of the parasympathetic nerves generally causes a decrease in atrial rate and contractile force, atrio-ventricular nodal conduction, and ventricular contractile force. Hence, selective stimulation of the autonomic nerves can provide a means for cardiac control for the purpose of modulating cardiac electrophysiology and/or cardiac hemodynamics.
The functions associated with the sympathetic and parasympathetic nervous systems are many and can be complexly integrated with each other. Thus, an indiscriminate stimulation of the sympathetic and/or parasympathetic nervous system to achieve a desired response in one physiological system may also result in an undesired response in other physiological systems. The cardiac plexus provides an alternative location within a patient's anatomy for selectively stimulating a portion of a patient's autonomic nervous system.
Thus, a need exists for an implantable lead including an electrode array capable of selectively and chronically stimulating the sympathetic and parasympathetic nervous system from an alternative site such as the cardiac plexus.